PROJECT SUMMARY/ABSTRACT Youth living with HIV (YLHIV) display elevated risk at every point of the Care Continuum. They face barriers to becoming engaged and retained in HIV care, show poor medication adherence, and thus often fail to achieve viral suppression. HIV-positive youth in the Deep South have particularly poor outcomes. South Carolina is one of nine states identified as ?key drivers? of the US HIV epidemic, and HIV rates for youth in South Carolina have risen rapidly in recent years (68% increase in past 15 years). Tailored interventions are urgently needed to improve outcomes for this population. One promising approach is to reach YLHIV via mobile Health (mHealth) technology, yet limited efforts have sought to tailor mHealth interventions to the needs of YLHIV in the Deep South. Thus the scientific objective of this K01 is to identify barriers experienced by YLHIV in South Carolina and then use findings to develop and pilot-test an mHealth intervention designed to increase engagement/retention in care and ART adherence. The career development objective of this K01 is to obtain the mentoring and training needed for a successful, high impact career investigating innovative ways to reduce HIV disparities among youth in the Southern US. This application is supported by a rigorous, highly productive research environment at the University of South Carolina and by a distinguished team of mentors. Collectively, mentors have expertise in psychological, behavioral, and socio-cultural aspects of HIV in the Deep South; the development of culturally-tailored HIV interventions; the use of mHealth to improve outcomes for YLHIV; factors related to a successful HIV Care Continuum; and rigorous intervention methodologies to test and enhance psychosocial and behavioral health interventions. Training experiences will provide expertise in formative assessment for intervention development; application of mHealth technologies to the HIV Care Continuum; intervention adaptation and development; theater testing methodology; innovative trial designs for mHealth interventions; and statistical/analytic skills necessary to assess intervention fidelity, acceptability, efficacy, and mechanisms of action. Training progression is linked to three specific research aims. In Aim 1, we will examine barriers to engagement/ retention in care and medication adherence for YLHIV in South Carolina. We will then use these findings to develop a tailored mHealth intervention to improve Care Continuum outcomes for YLHIV in the Deep South (Aim 2) by integrating several promising mHealth strategies. In Aim 3, we will evaluate the feasibility, acceptability, and usability of the mHealth intervention with a six-month pilot trial with 40 YLHIV in South Carolina. The project is relevant to NIMH priorities as it will bring together key stakeholders including patients, providers, and researchers to produce a developmentally and culturally tailored behavioral health intervention that can optimize clinical outcomes. It also aims to use an innovative service delivery model (i.e., mHealth technology) with a diverse population (i.e., YLHIV in the Deep South) in order to overcome traditional shortcomings of mental and behavioral healthcare.